1. Where’s The Peak? Observations of Tidal Marsh Diversity Along The Patuxent and Nanticoke RiversBy
Peter Sharpe and Andrew H. Baldwin
The University of Maryland
Department of Environmental Science and Technology
May-August 2006

2. Research Objectives
Describe plant species richness across a salinity gradient (fresh-brackish) in tidal marshes of two Chesapeake Bay Tributaries
Salinity
Richness
Fresh
Brackish
Transitional
Richness
Salinity

3. Patuxent River
Washington D.C.

4. Patuxent River Watershed Features
Watershed Size – 2,356 km2
Gradient Length – 47 km
Mean Tidal Range at Jug Bay – 0.73 m
Land Use:
30% Agricultural
40% Forest
20% Urban
10% Other Land Uses
Number of Survey Plots - 13

5. Patuxent River
Washington D.C.
Nanticoke River

6. Nanticoke River Watershed Features
Watershed Size – 2,136 km2
Gradient Length – 56 km
Mean Tidal Range at Sharptown, MD – 0.76 m
Land Use:
48% Agricultural
41% Forest
2% Urban
8% Other Land Uses
Number of Survey Plots - 16

7. Patuxent and Nanticoke River Study Sites
Patuxent River Gradient – 47 km
Nanticoke River Gradient – 56 km
Seaford, DE
Jug Bay
Bivalve Harbor
Benedict

8. Methods
Vegetation surveyed using nested plot design consisting of a series of 10x10 m modules (Peet et al. 1998) 10 2 3 7 4 6 5 8 9 1
20 m
50 m
Nest (Depth)
Dimensions
Area
Depth 5
10 cm x 10 cm
0.01 m2
Depth 4
32 cm x 32 cm
0.1 m2
Depth 3
1m x 1m
1 m2
Depth 2
3.16m x 3.16m
10 m2
Depth 1
10m x 10m
100 m2
Residuals
20 m x 50m
1,000 m2
GPS Reading
Piezometer Location
SCT Reading

9. Typical Sampling Location
High Marsh
Levee
Low Marsh
Surveyed Area
10 m

10. Nanticoke River Species Richness Results (May-August) Residual Depth
1000 m2 Survey Area

11. Patuxent River Species Richness Results (May-August) Residuals
1000 m2 Survey Area

12. Conclusions
Nanticoke River data show no immediate reduction in richness, actually an increase along the Nanticoke up to mean soil salinity of 3-4 ppt (peak observed at 0.8 ppt soil salinity)
Patuxent River data show slight peak in June within limits of salt intrusion followed by maintenance of species richness along gradient up to 3 ppt
Periodic salt water stress could promote coexistence of freshwater and brackish species
Other potential factors: soil nutrient concentrations, marsh hydroperiods, toxicants, invasive species

13. Acknowledgements
Project funding provided by the Maryland/D.C. Chapter of The Nature Conservancy through a Biodiversity Conservation Research Fund Grant
Special thanks to Dr. Andrew Baldwin, Dr. David Tilley, Daniel Marcin, Robbie Vocke, Krissy Rusello, Douglas Rau, and Katherine Sharpe